JP3256064B2 - Method of forming resist pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern, and more particularly to a method for forming a resist pattern which is modified after development.

[0002] The integration and miniaturization of semiconductor integrated circuit devices (ICs) are increasing more and more. In IC manufacturing technology,
Smaller size patterns are required. In a 64-Mbit DRAM, the processing size is 0.3 to 0.4.
Processing of μm is required.

[0003]

2. Description of the Related Art A general resist pattern is formed by selectively irradiating an applied resist film with ultraviolet rays for exposure, and selectively developing and removing an exposed area or a non-exposed area. Exposure is performed by reducing the pattern on a mask (reticle) to 1/10 or 1/5 with a projection lens and forming an image on a resist film. The resolution is determined by the wavelength of the ultraviolet light used for exposure, the opening angle of the projection lens, and the like.

In order to improve the resolution, it is necessary to increase the aperture angle or shorten the wavelength. However, increasing the aperture angle decreases the depth of focus. In order to perform highly accurate exposure on a substrate having a step, it is desired that the depth of focus is deeper than a certain level.

[0005] The remaining possibility is to shorten the wavelength of the ultraviolet light used. Therefore, the wavelength for exposure is shortened from mercury g-line to i-line, and further shortened to KrF laser light and ArF laser light. However, as the wavelength becomes shorter, restrictions on optical members and the like used become stricter.

As another method for improving the dispersibility, a phase shift exposure method has been developed. Light having a phase different from that of the main beam for exposure is caused to interfere by overlapping and exposing a pattern end portion where the main beam spreads by diffraction, and blurring of the pattern can be prevented by reducing the light intensity. However, since it is necessary to form two or more types of light having a phase difference, the structure of the mask is complicated.

[0007]

As described above,
Although it is desired to form a finer resist pattern, its realization is not easy.

An object of the present invention is to provide a method for forming a resist pattern which can form a fine resist pattern by a simple method.

[0009]

A method of forming a resist pattern according to the present invention comprises forming a resist film by applying a resist containing a phenolic hydroxyl group whose volume can be increased by a chemical reaction to the surface of a workpiece. Exposing and developing the applied resist film to form a pattern having openings, and increasing the volume of the patterned resist film by chemically reacting with the phenolic hydroxyl group. Contacting a fluid containing acetyl chloride that can be formed, a reaction step of chemically reacting phenolic hydroxyl groups and acetyl chloride, and a heating flow step of heating the resist film to generate a flow after the reaction step, The size of the opening of the resist film is changed.

[0010]

The resist film containing the component A is exposed and developed to form an opening, and then a fluid containing the component B is brought into contact with the resist film to chemically react the components A and B in the resist. Inflate the volume of the membrane. When the resist film undergoes volume expansion, the size of the opening is reduced. Further, the shape is changed by heating the resist film to generate a flow. Therefore, an opening having a smaller size than the exposed and developed opening can be formed.

[0011]

EXAMPLES The present inventors have discovered that the volume of a resist film can be expanded by causing a certain reaction to occur in a resist film formed on an object to be processed.

In recent years, as a high-performance resist widely used, there is a resist developable with an aqueous alkali solution.
For example, a novolak-based positive resist is used. Such a resist has a large amount of phenolic hydroxyl groups in the composition. When the hydroxyl group and a predetermined reactant are chemically reacted, the resist composition changes and the volume can be increased.

The composition of the resist that undergoes such a chemical reaction is not limited to phenolic hydroxyl groups. Further, the resist is not limited to those described above. It is also possible to add a component capable of performing such a chemical reaction to the resist composition.

A typical reaction that causes an increase in volume in the reaction with a phenolic hydroxyl group is esterification of the hydroxyl group. Examples of the ester include a carboxylic acid ester and a thiocarboxylic acid ester. When the phenolic hydroxyl groups are esterified, the volume of the resist increases.

Taking a carboxylic acid ester as an example, esterification of a hydroxyl group is achieved by acylation of a hydroxyl group, and an acylating reagent can be used as a reactant. The reaction between acetyl chloride, which is a typical acylating reagent, and cresol novolac, which is a base resin for a resist, can be represented as follows.

[0016]

Embedded image

Embodiments FIGS. 1A to 1D show a method of forming a resist pattern according to an embodiment of the present invention.

As shown in FIG. 1A, a resist film 2 is formed on the surface of a substrate 1. The resist film 2 is formed of a novolak i-line resist (trade name: ZIR9000, manufactured by Zeon, Japan). This resist material is alkali developable and has a phenolic hydroxyl group.

Using an exposure system as shown in FIG. 2, the resist film 2 is selectively irradiated with an irradiation beam 3 to expose the resist film 2. The irradiation beam 3 is, for example, i-ray ultraviolet rays of a mercury lamp.

FIG. 2 shows a standard exposure system. A light beam 12 emitted from a light source 11 including a fly-eye lens is condensed by an illumination optical system 13 including an illumination lens, and
Irradiate 4. On the mask 14, a light-shielding pattern is selectively formed. The light beam passing through the mask 14 is focused by a projection optical system 15 including a projection lens, and is imaged on the surface of the wafer 16 including the substrate 1 and the resist film 2.

The resolution of such an exposure system is determined by the wavelength of the light beam 12 emitted from the light source 11, the aperture angle of the projection optical system 15, and the like. That is, the latent image that the irradiation beam 3 can form in FIG. 1A is larger than a certain dimension.

As shown in FIG. 1B, the exposed resist film 2 is developed with an alkaline developer, and the exposed portion is removed to form an opening 4. As described above, the minimum size of the opening 4 is limited by the resolution of the exposure system.

Next, the wafer 16 is placed in a reactor as shown in FIG. 3, and an acetyl chloride gas is flowed to cause a reaction between the resist and acetyl chloride. In FIG. 3, an acetyl chloride solution 22 is contained in a bubbler container 23. The pipe 27 inserted into the acetyl chloride solution 22 includes:
Gases such as N ₂ and air are supplied. This gas is bubbled in the acetyl chloride solution 22 and supplied to the reaction chamber 25 through a pipe 28 arranged above the liquid level.

In the reaction chamber 25, the wafer 16
Are placed on a hot plate 26. Wafer 16
By heating the acetyl chloride gas while heating
The reaction between the resist film on the wafer 16 and acetyl chloride proceeds.

The gas after the reaction is discharged from the exhaust pipe 24. In order to efficiently promote the reaction between the novolak-based resist and acetyl chloride, the wafer is preferably heated to about 90 ° C. or higher.

When the novolak-based resist and acetyl chloride react according to the above reaction formula, the molecular weight increases and the volume increases. FIG. 1C shows the resist film 2a whose volume has been expanded by the reaction with acetyl chloride. Since the resist film 2a tends to expand in all directions due to volume expansion, as shown in FIG.
Is smaller than the opening 4 shown in FIG.

In a portion where the resist film 2a is in contact with the substrate 1, the resist film 2a
Since a holding force acts on the resist film 2a, the resist film 2a does not expand much in the lateral direction at the interface.

However, since the opening 4a is a free space above the resist film 2a, the resist film 2
a also expands in the lateral direction, forming a medium swelling shape as shown in the figure.

FIGS. 4A and 4B show Fourier spectral infrared absorption spectra of the resist film before and after the reaction between the novolak resist and acetyl chloride. FIG.
(A) is the spectrum before the reaction, and FIG. 4 (B) is the spectrum after the reaction. The measurement sample is obtained by reacting a ZIR9100 resist film having a thickness of 1.12 μm formed on a Si wafer with acetyl chloride.

In the spectrum of the reagent shown in FIG.
The absorption of the hydroxyl group existing in the wave number region of 00 to 3600 cm ^-1 has almost disappeared in the spectrum after the reaction with acetyl chloride in FIG. Therefore, it can be considered that the resist film after the reaction treatment reacted almost completely (over the entire thickness). Further, the absorption based on an ester of about 1200 cm ^-1 and 1763cm ^-1 which were not present prior to the reaction, which clearly appear in the spectrum after reaction of FIG. 4 (B).

The resist film 2a after the reaction shown in FIG.
Indicates an inflated shape at the opening 4a. In order to perform high-precision patterning, the opening of the resist pattern preferably has a side surface that is as close to vertical as possible.
Therefore, as shown in FIG. 1D, the resist film after the reaction is heated. In the case of a reaction product of a novolak resin and acetyl chloride, the heating temperature is desirably about 130 ° C. or higher.

By this heating, the flow of the resist film 2a increases, causing a flow as shown in FIG. 1 (D), and changing the shape so that the opening has a substantially vertical side surface. That is, the resist film 2b expands in the lateral direction even at the interface between the substrate 1 and the resist film 2b. The effective size of the opening 4b is further reduced.

As described above, after exposing and developing the novolak-based resist film, it reacts with acetyl chloride, and further generates a flow, whereby an opening 4b having a smaller dimension than the developed opening 4 can be obtained. Although the case where the reaction process and the flow process are generated separately has been described, the reaction and the flow can be simultaneously generated by increasing the temperature of the reaction process to about 130 ° C. or more.

FIG. 5 schematically shows changes in the resist pattern according to the above embodiment. The resist pattern can be roughly classified into a remaining independent pattern such as a line of a line-and-space pattern and a punched pattern such as a contact hole whose periphery is surrounded by a resist film.

FIGS. 5A1 and 5B1 schematically show the shapes of an independent pattern and a blank pattern after exposure and development. A resist film pattern 2 is formed on a substrate 1 to constitute an independent pattern and a hole pattern.

When such a resist pattern is reacted with a predetermined component (for example, acetyl chloride), the resist pattern shown in FIG.
2), it changes to a pattern shape as shown in (B2).
On the contact surface with the substrate 1, the resistance is strong, so that the expansion of the resist film in the horizontal direction is restricted, and the resist pattern mainly expands in the horizontal and upward directions at the upper part. In particular, the independent pattern is in an inflated state as shown in FIG.

In the case where the size of the punch pattern is small, FIG.
As shown in (B1), the side surface of the opening after development tends to have a certain degree of inclination. In particular, the side surface of the resist film is unlikely to be vertical at the bottom of the hole. For this reason, the side surface of the resist film 2 after the reaction tends to be in a middle swelling state due to the expansion, but offsets with the slope shape of the resist film before the reaction, so that the side surface is relatively vertical as shown in FIG. Easy side.

After the reaction, when the resist film is further heated to cause a flow in the resist film, the independent pattern and the cut pattern change to the shapes shown in FIGS. 5 (A3) and (B3). That is, the resist film 2 of the independent pattern is released from the swelling state, and has a nearly vertical side surface.
Also, in the punch pattern, the side surface of the resist film is extruded into the opening by the flow, and the size of the opening is reduced.

In the case of the independent pattern, the pattern size increases due to the reaction and flow, and in the case of the blank pattern, the pattern size decreases due to the reaction and flow. In the sense of creating a pattern having a size equal to or smaller than the resolution of the optical system, the above-described embodiment has a greater utility than the punched pattern.

The results of experiments using a novolak i-line resist (trade name: ZIR9000, manufactured by Zeon, Japan) will be described below. FIGS. 6A and 6B show pattern shapes of experimental samples. FIG. 6A shows the shape of the line and space pattern. A resist film was formed on the Si substrate 5 and exposed and developed to form a line pattern 6a. An opening (space) 7a is formed between the plurality of line patterns 6a.
FIG. 6B shows the pattern shape of the hole pattern.
A circular opening (hole) 7b is formed in the resist film 6b.

In the case of the line-and-space pattern, the horizontal dimension of both the line pattern 6a and the opening 7a is 0.6 μm, and in the case of the hole pattern, the circular opening 7b
Was 0.6 μm in diameter. After forming such a resist pattern, a reaction with acetyl chloride was caused under various conditions.

FIGS. 7A and 7B are cross-sectional photographs of the resist pattern of Sample 1 exposed and developed. FIG.
(A) is a photograph of a line and space pattern,
The magnification is 21000 times. FIG. 7B is a cross-sectional photograph of the hole pattern, and the magnification is 41900 times.

FIGS. 8A and 8B are cross-sectional photographs of the resist pattern of Sample 2 heated at 150 ° C. for 2 hours in a nitrogen atmosphere after development. FIG. 8A is a cross-sectional photograph of the line and space pattern, and the magnification is 1920.
It is 0 times.

FIG. 8B is a cross-sectional photograph of the hole pattern, and its magnification is 38,300. The size of the resist pattern hardly changed by heating at 150 ° C. for 2 hours. 7 (A), (B), FIG. 8 (A),
(B) is shown for comparison with a resist pattern when a reaction is caused with acetyl chloride described below.

FIGS. 9A and 9B show the results at 90 ° C. for 2 hours.
4 shows a resist pattern of Sample 3 in which a reaction with acetyl chloride was caused using nitrogen as a carrier gas. FIG. 9 (A)
Is a cross-sectional photograph of the line and space pattern, and the magnification is 21900 times. FIG. 9B is a cross-sectional photograph of the hole pattern, and the magnification is 43700 times.

The photograph of the line and space pattern in FIG. 9A clearly shows the barrel shape in the middle of the line pattern swelling in the horizontal direction. On the other hand, the hole pattern in FIG. 9B does not have a swollen shape in the middle of the resist film, but the resist pattern in FIG. 7B and FIG. Compared to the shape, it can be seen that it expands in the lateral direction due to volume expansion.

FIGS. 10A and 10B show resist patterns of Sample 4 reacted with acetyl chloride at 110 ° C. for 2 hours using nitrogen as a carrier gas. FIG. 10 (A)
Is a cross-sectional photograph of the line and space pattern, and the magnification is 21200 times. FIG. 10B is a cross-sectional photograph of the hole pattern, and the magnification is 42,400. Also in this case, the same change in the shape of the resist pattern as in FIGS. 9A and 9B is observed.

FIGS. 11A and 11B are cross-sectional photographs of the resist pattern of Sample 5 reacted with acetyl chloride at 130 ° C. for 2 hours using nitrogen as a carrier gas. FIG. 11A is a cross-sectional photograph of the line and space pattern, and the magnification is 20200 times. FIG. 11 (B)
Is a cross-sectional photograph of the hole pattern, the magnification of which is 40.
It is 400 times.

The line shape of the line-and-space pattern shown in FIG. In the cross-sectional shape of the hole pattern in FIG. 11B, the side surface rises more nearly vertically, and shows a slight tendency to bulge.

FIGS. 12A and 12B are cross-sectional photographs of the resist pattern of Sample 6 reacted with acetyl chloride at 130 ° C. for 6 hours using nitrogen as a carrier gas. FIG. 12A is a cross-sectional photograph of the line and space pattern, and the magnification is 19100 times. FIG. 12 (B)
Is a cross-sectional photograph of the hole pattern, the magnification of which is 38.
It is 100 times.

In these photographs, it is recognized that the line pattern and the hole pattern are alleviated in the inflated shape. Further, the width of the space portion is narrow, which indicates that the resist has expanded in the lateral direction and a flow has occurred.

FIGS. 13A and 13B are cross-sectional photographs of the resist pattern of Sample 7 reacted with acetyl chloride at 140 ° C. for 2 hours using nitrogen as a carrier gas. FIG. 13A is a cross-sectional photograph of the line and space pattern, and the magnification is 20100 times. FIG.
(B) is a cross-sectional photograph of the hole pattern, and the magnification is 40200 times.

In FIG. 13 (A), further expansion of the resist film is observed, and a barrel-like shape with a medium swelling is observed. The effect of flowing the resist may be weaker at 140 ° C. for 2 hours than at 130 ° C. for 6 hours. FIG. 13 (B)
Shows a substantially vertical side surface as in FIG. 12B, and the width of the opening is further narrowed.

FIGS. 14 (A) and (B) show the results at 150 ° C.
4 shows a cross-sectional photograph of a resist pattern of Sample 8 in which acetyl chloride was reacted with nitrogen as a carrier gas for a minute.
FIG. 14A is a cross-sectional photograph of the line and space pattern, and the magnification is 18500 times. FIG.
(B) is a cross-sectional photograph of the hole pattern, the magnification of which is 36,900.

The cross-sectional shape of the line pattern shown in FIG. 14 (A) shows a tendency to slightly expand at the lower part, but the side surface is almost vertical. The effect of flowing the resist is 140 ° C2
Time and 130 ° C. for 6 hours. The cross-sectional shape of the hole pattern in FIG. 14B is somewhat asymmetrical in the left and right directions, but the width of the hole is narrow.

FIGS. 15A and 15B are cross-sectional photographs of the resist pattern of Sample 9 in which the reaction time for reacting with acetyl chloride using nitrogen gas as a carrier gas at 150 ° C. was extended to 30 minutes.

FIGS. 16 (A) and 16 (B) show the results at 150 ° C.
Sample 10 in which the reaction time was extended to 1 hour
3 shows a cross-sectional photograph of the resist pattern of FIG. FIG. 17 (A),
(B) shows a cross-sectional photograph of the resist pattern of Sample 11 in which the reaction treatment time was further extended to 1.5 hours at 150 ° C.

FIGS. 18 (A) and 18 (B) show the results at 150 ° C.
3 shows a cross-sectional photograph of the resist pattern of Sample 12 in which the reaction time was further extended to 2 hours. FIG.
As is clear from the photographs of (A), (B) to FIG. 18 (A), (B), when the reaction time is extended at 150 ° C.,
The lateral spread of the resist pattern gradually increases, and from the middle bulging cross-sectional shape to a shape having a substantially vertical side surface, to a tapered cross-sectional shape gradually expanding further downward. It can be seen that the size of the opening gradually narrows with increasing reaction time.

The experimental results described above are shown in Table 1 below.
Are shown together. The measured resist film thickness is also shown.
The effect of reducing the hole size is shown in four stages: small (+), medium (++), large (++++), and extra-large (++++), the details of which are shown by the photographs described above.

[0060]

[Table 1]

In Table 1, No indicates a sample number, processing conditions indicate processing conditions after development, temperature indicates a heating temperature in the processing, and time indicates a processing time.

As is clear from the above experimental results, when the novolak-based resist reacts with acetyl chloride, the volume of the resist film expands, and the diameter of the hole pattern decreases. In the case of the line and space pattern, the line pattern becomes thick and the width of the space portion becomes small.

The case where the novolak resist and acetyl chloride are reacted at a temperature of 90 ° C. or higher has been described.
A temperature of 90 ° C. or higher is not always necessary. When the temperature is relatively low, the swelling shape of the resist pattern after the reaction is apparent, but by setting the temperature to 130 ° C. or higher, the swelling shape is gradually alleviated.
This is presumably because the resist was softened by heating and also flowed (flowed) in the lateral direction.

When the exposed and developed side faces of the resist pattern are almost vertical, the resist pattern after the reaction has a medium swelling, but by generating a flow, a side face that is more vertical can be obtained.

When the side surface of the resist pattern after development is a slope, the side surface of the resist pattern can be made more vertical by reaction with acetyl chloride. Further, if the heating is further performed, the opening of the resist pattern can be narrowed. Heating at about 130 ° C. or higher is preferred to create a flow.

Embodiment FIGS. 19A to 20C show a method of forming a resist pattern according to a more specific embodiment.

As shown in FIG. 19A, a field oxide film 32 is selectively formed on the surface of a silicon substrate 31. An insulated gate structure having a gate insulating film 33 and a gate electrode 34 is formed in an active region surrounded by a field oxide film 32, and ion implantation is performed to form lightly doped source / drain regions 37.

Thereafter, a sidewall oxide region 35 is formed on the side surface of the insulated gate electrode, and an insulated gate electrode structure 36 is completed. Further, ion implantation is performed using the insulated gate electrode structure 36 as a mask to form heavily doped source / drain regions 38. Thereafter, a silicon oxide film 39 is formed on the surface to insulate the gate electrode. A resist film 42 is formed on the silicon oxide film 39, and a source /
The opening for the contact in the drain region is exposed.

FIG. 19B shows a resist pattern after development. By developing and removing the exposed portion, the unexposed portion 42a of the resist film 42 remains. Thus, the hole pattern 43a is formed above the source / drain region.

As shown in FIG. 19C, an acetyl chloride gas is flowed over the resist film 42a having the hole pattern 43a to cause an acylation reaction with hydroxyl groups of the resist film. Resist film 42 that has undergone an acylation reaction with acetyl chloride
a expands to become a resist film 42b. Here, the opening pattern 43b of the resist film is the opening pattern 4 after the development.
The size is smaller than 3a.

The resist mask 42b expanded as described above.
Is used as an etching mask, and the silicon oxide film 39 disposed thereunder is patterned. FIG.
(A) shows a step of forming an opening 43c by anisotropically etching the silicon oxide film 39 disposed under the resist mask 42b as an etching mask. Reduced opening dimension 43 of volume-expanded resist pattern 42b
According to b, the silicon oxide film 39 (A) is etched. After etching, the remaining resist mask 42
b is removed.

As shown in FIG. 20B, an electrode layer 44 of polycrystalline silicon, high melting point metal, aluminum or the like is deposited on the wafer including the formed opening 43c. Electrode layer 4
4 is in ohmic contact with the source / drain regions 38a, 38b. After that, a resist pattern is formed on the electrode layer 44, and the electrode layer 44 is patterned.

FIG. 20C shows an electrode pattern obtained after patterning. By removing unnecessary portions of the electrode layer 44, an electrode 44a connected to the source / drain region 38a and an electrode 44b connected to the source / drain region 38b are obtained.

According to the above-described embodiment, a sample is formed,
An experiment was performed. A resist film was formed using a novolak-based resist. After forming the resist film, prebaking was performed at 90 ° C., and exposure and development were performed to obtain a resist pattern.
FIG. 21 shows the resist pattern at this stage.

The resist pattern thus formed has
The reaction was carried out at 90 ° C. for 30 minutes by bringing acetyl chloride gas into contact with nitrogen as a carrier gas. Thereafter, a heat treatment was further performed at 170 ° C. for 2 hours.

FIG. 22 shows the cross-sectional shape of the resist pattern at this stage. It is clearly recognized that the diameter of the hole pattern is small. Further, by irradiating the resist film with ultraviolet rays, the fluidity of the resist film can be increased.

[0077] Example Similarly prepared resist pattern of Example above, is irradiated with ultraviolet rays on the entire surface using a UV lamp. Thereafter, an acetyl chloride gas is brought into contact with the resist pattern at 90 ° C. for about 30 minutes using nitrogen as a carrier gas to perform a reaction treatment. Further, a heat treatment at 150 ° C. to 170 ° C. is performed.

The result of the treatment at 150 ° C. for 2 hours is
As shown in FIG. It can clearly be seen that the diameter of the hole pattern has been reduced. When the heat treatment at 170 ° C. was performed for about 30 minutes, the hole pattern changed as shown in FIG. The holes are completely buried because the fluidity of the resist has increased too much.

From the above experimental results, it can be seen that the resist can be easily flowed by irradiating the resist pattern with ultraviolet rays.

COMPARATIVE EXAMPLE After a resist pattern was formed in the same manner as in the above-described embodiment, the resist pattern was irradiated with ultraviolet rays, and without being subjected to acetyl chloride treatment.
Heat treatment was performed at about 30 ° C. for about 30 minutes. FIG. 25 shows the result. It can be seen that the diameter of the hole pattern was reduced, but the resist film thickness was significantly reduced.

Although the case of the esterification reaction with acetyl chloride has been described above, other esterification reactions can be used. For example, a sulfonic esterification reaction can be used.

As the ultraviolet light source, for example, a mercury lamp can be used. An acetyl chloride gas was reacted with the resist mask shown in FIG. 21 at 150 ° C. for about 2 hours using nitrogen as a carrier gas. For comparison, a wafer which was not subjected to ultraviolet exposure was also heated and reacted in the same manner.

FIG. 26 is a cross-sectional photograph of a resist pattern obtained by reacting with acetyl chloride using nitrogen as a carrier gas after the entire surface exposure with ultraviolet rays. It is observed that when the resist film is exposed to ultraviolet light, the hole pattern is likely to be reduced. In the example, the acetyl chloride treatment was performed after the irradiation with the ultraviolet light. However, the effect is equivalent even if the acetyl chloride treatment is performed while irradiating the ultraviolet light.

FIG. 27 shows a cross-sectional photograph of the resist pattern when no ultraviolet exposure was performed. An acetyl chloride gas is applied to the exposed novolak resist at 180 ° C. for 2 minutes, 5 minutes, 10 minutes, 20 minutes, 6 minutes using nitrogen as a carrier gas.
After exposure for 0 minutes, the absorption spectrum of each sample was measured.

FIG. 28 shows the measurement results. 1763cm
The absorption of ^-1 indicates the absorption of the reaction product of the novolak resin and acetyl chloride in the resist. FIG. 29 shows the relationship between the intensity of the absorption peak and the reaction time. Absorption is about 15
It can be seen that the reaction is almost saturated within minutes, and the reaction is almost completed in about 15 minutes.

EXAMPLE As in the above-described example, a photoresist film is formed and exposed and developed to obtain a resist pattern.

FIG. 30 shows the resist pattern thus created. An acetyl chloride gas using nitrogen as a carrier gas is reacted with the resist pattern at 150 ° C. for 15 minutes. FIG. 3 shows an example of a resist pattern after the reaction.
It is shown in FIG.

The reaction is carried out at 150 ° C. for 30 minutes with acetyl chloride gas using nitrogen as a carrier gas. FIG. 32 shows the shape of the resist pattern after the reaction. After reacting with acetyl chloride gas at 150 ° C. for 15 minutes, the gas was cut off and the mixture was heated in air at 170 ° C. for 15 minutes. FIG. 33 shows an example of the resist pattern after heating.

The reaction at 150 ° C. for 15 minutes causes the resist pattern to expand, forming a medium swelling shape. 150 ° C 30
In the reaction for a minute, the bottom of the resist pattern expands, and an edge that falls almost vertically is formed.

After heating at 150 ° C. for 15 minutes and then at 170 ° C. for 15 minutes, almost the same shape is obtained. The case where a novolak-based resist is used as the resist material has been described above, but the resist is not limited to the novolak-based resist.

Example A resist film is formed using a resist material in which a photoacid generator is mixed with a resin obtained by reacting acetal with polyvinylphenol. The resist pattern after exposure and development is reacted with acetyl chloride and subjected to a heat treatment.

As a result, the volume of the resist pattern is 0 to
It increased by 20%. Also, a reduction in the hole diameter of the hole pattern and an increase in the line pattern of the line and space pattern were clearly observed.

A resist material obtained by mixing a photoacid generator with a resin obtained by reacting acetal with polyvinylphenol is as follows:
It can be represented by the following chemical formula:

[0094]

Embedded image

Example A resist film was formed by using a resist material in which a photoacid generator was mixed with a resin obtained by converting t-BOC into polyvinylphenol. Acetyl chloride is reacted with the resist pattern after exposure and development, and heat treatment is performed. As a result, the volume is 2 to
It increased by 3%.

[0096]

Embedded image

The case where the resist film and the reactant are reacted by heating has been described above, but the reaction mode is not limited to the above. For example, the chemical reaction can be promoted by plasma.

FIG. 34 schematically shows the structure of a plasma reactor. A wafer 51 having a resist mask formed on the surface by exposure and development is placed on a stage 55.
A shield plate 54 is arranged above the stage 55 to electrically shield the wafer 51. Note that the shield plate 54 has a wire mesh or mesh shape, and gas can freely pass therethrough.

The plasma chamber 5 is located above the shield plate 54.
2 are formed. The plasma formed by the magnetron 53 is supplied to the plasma chamber 52 via a tuner 58. A reaction gas such as acetyl chloride is supplied from the reaction gas inlet 56.

In the plasma chamber 52, the supplied plasma gas is excited by the microwave supplied from the magnetron 53 to generate plasma. The generated plasma is supplied as a radical onto the wafer 51 via the shield plate 54. After that, the plasma gas
Air is exhausted from the exhaust port 57.

The substrate 51 is heated to 70 ° C., and NF ₃ gas is supplied from the reaction gas inlet 56 to form F-type plasma. The wafer 51 is exposed to this F-system plasma for 5 minutes,
The system plasma reacts with the resist film on the wafer 51.

The volume of the resist film after the reaction clearly increased. It is considered that hydroxyl groups contained in the resist film reacted with other plasma. The dimension of the hole pattern formed in the resist pattern became smaller.

As described above, the size of the opening in the resist pattern can be reduced by causing a chemical reaction in the exposed resist pattern to cause volume expansion. As the reactant, a carboxylic acid halide represented by R-CO-X (where R is an organic group having 1 to 20 carbon atoms and X is a halogen element) may be used. Acetyl chloride is a typical example. As a reactant, R
—SO ₂ —X (where R is an organic group having 1 to 20 carbon atoms, X
May be halogenated sulfonic acid halides. Also, R ₁ —CO—O—CO—R ₂ or

Embedded image (However, R, R ₁ , and R ₂ may each be an organic group having 1 to 20 carbon atoms). Further, one or more of NF ₃ , CF ₄ , F ₂ , ClF ₃ and SF ₆ may be used.

For example, a hole pattern of 0.2 to 0.25 μm can be formed by exposure using an i-line having a wavelength of 0.365 μm. Kr with a wavelength of 0.248 μm
If an F excimer laser is used, a finer hole pattern can be formed. Of course, a pattern having a larger dimension may be formed. Even in such a case, the size of the resist pattern after exposure and development can be increased, so that there is a margin in mask accuracy and exposure accuracy.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example,
The resist material may be of any composition as long as its volume can be increased by a chemical reaction.
The reactant that reacts with the resist may be any substance that can increase the volume of the resist.

It will be apparent to those skilled in the art that various changes, improvements, combinations, and the like can be made.

[0107]

As described above, according to the present invention,
A fine resist pattern can be easily formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a method of forming a resist pattern according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an exposure system.

FIG. 3 is a schematic sectional view showing a configuration of a reaction apparatus.

FIG. 4 is a graph showing absorption spectra of a resist film before and after a reaction.

FIG. 5 is a cross-sectional view schematically showing a change in the shape of a resist film due to a reaction.

FIG. 6 is a plan view showing a resist pattern of an experimental sample.

FIG. 7 is a micrograph of a thin film showing experimental results.

FIG. 8 is a micrograph of a thin film showing experimental results.

FIG. 9 is a micrograph of a thin film showing experimental results.

FIG. 10 is a micrograph of a thin film showing experimental results.

FIG. 11 is a micrograph of a thin film showing experimental results.

FIG. 12 is a micrograph of a thin film showing experimental results.

FIG. 13 is a micrograph of a thin film showing experimental results.

FIG. 14 is a micrograph of a thin film showing experimental results.

FIG. 15 is a micrograph of a thin film showing experimental results.

FIG. 16 is a micrograph of a thin film showing experimental results.

FIG. 17 is a micrograph of a thin film showing experimental results.

FIG. 18 is a micrograph of a thin film showing experimental results.

FIG. 19 is a schematic sectional view illustrating a method of forming a resist pattern according to an embodiment of the present invention.

FIG. 20 is a schematic sectional view illustrating a method of forming a resist pattern according to an embodiment of the present invention.

FIG. 21 is a micrograph of a thin film showing experimental results.

FIG. 22 is a micrograph of a thin film showing experimental results.

FIG. 23 is a micrograph of a thin film showing experimental results.

FIG. 24 is a micrograph of a thin film showing experimental results.

FIG. 25 is a micrograph of a thin film showing experimental results.

FIG. 26 is a micrograph of a thin film showing experimental results.

FIG. 27 is a micrograph of a thin film showing experimental results.

FIG. 28 is a graph of an infrared absorption spectrum showing experimental results.

FIG. 29 is a graph showing a change in absorption intensity with respect to a reaction time.

FIG. 30 is a micrograph of a thin film showing experimental results.

FIG. 31 is a micrograph of a thin film showing experimental results.

FIG. 32 is a micrograph of a thin film showing experimental results.

FIG. 33 is a micrograph of a thin film showing experimental results.

FIG. 34 is a schematic sectional view showing a configuration of a plasma reactor.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 resist film 3 irradiation beam 4 aperture 5 substrate 6 resist film 7 aperture 11 light source 12 light beam 13 illumination optical system 14 mask 15 projection optical system 16 wafer 22 acetyl chloride solution 23 bubbler container 24 exhaust duct 25 reaction chamber 26 hot plate 31 Silicon substrate 32 Field oxide film 33 Gate insulating film 34 Gate electrode 35 Side wall oxide region 36 Insulated gate electrode structure 37 LDD region 38 Source / drain region 39 Silicon oxide film 42 Resist film 44 Electrode layer 51 Wafer 52 Plasma chamber 53 Magnetron 54 Shield Plate 55 stage 56 reaction gas inlet 57 exhaust outlet 58 tuner

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masao Kanazawa 1015 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Hiroshi Kudo 1015 Ueodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited ( 56) References JP-A-5-166717 (JP, A) JP-A-2-156244 (JP, A) JP-A-51-150279 (JP, A) JP-A-6-250379 (JP, A) ) Surveyed field (Int.Cl. ⁷ , DB name) G03F 7/40 H01L 21/027

Claims (6)

(57) [Claims] 1. A step of applying a resist containing a phenolic hydroxyl group whose volume can be increased by a chemical reaction to the surface of a workpiece to form a resist film, and exposing and developing the applied resist film. A patterning step of forming a pattern having an opening, and contacting the patterned resist film with a fluid containing acetyl chloride, which can increase the volume by chemically reacting with the phenolic hydroxyl group, and the phenolic hydroxyl group Forming a resist pattern that changes a dimension of an opening of the resist film, comprising: a reaction step of chemically reacting acetyl chloride; and a heating flow step of heating the resist film to generate a flow after the reaction step. Method. 2. The method according to claim 1, wherein said heating flow step is performed simultaneously with said reaction step. 3. The method according to claim 1, wherein the reaction step is performed at a temperature of 90 ° C. or higher. 4. The method for forming a resist pattern according to claim 1, wherein said heating flow step is performed at a temperature of 130 ° C. or higher. 5. The method according to claim 3, wherein the resist is a novolak resist. 6. The resist pattern according to claim 1, further comprising a step of irradiating the resist film with ultraviolet rays after the patterning step, and performing a reaction step of contacting the fluid containing the acetyl chloride after or simultaneously with the ultraviolet irradiation step. Formation method.